Boring machine

ABSTRACT

In a boring machine, rotation of a motor is transferred to a pipe spindle and a shaft, a cutting edge feeding mechanism arranged side by side with the pipe spindle moves the shaft toward a workpiece and a cutting edge attached to an end of the shaft drills a hole in the workpiece. The cutting edge feeding mechanism slidably but non-rotatably supports a chain holder around an outer circumference of the pipe spindle. A sprocket wrapped around by a chain is rotated by a handle to move the shaft. The radius of rotation of the handle is reduced to slowly move the shaft. The maximum torque of the motor rotating the shaft is controlled. The number of cutting edges falls within a range from six to eight.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in boring machines fordrilling holes for branch line on one of a main line of water pipe and agas pipe for branch line.

2. Description of the Related Art

In a conventional method of attaching a branch line to one of awater-pipe main line and a gas-pipe main line, a saddle corporation stopis typically fixed onto the main line, and a hole is drilled on the pipewith a boring machine mounted on the saddle corporation stop. A varietyof boring machines has been proposed. For example, Japanese UnexaminedPatent Application Publication No. 2002-66819 discloses one boringmachine. In the disclosed boring machine, a cutting edge feedingmechanism using a chain is employed, and a cutting edge rotated by amotor is raised and lowered by handle operation.

More in detail, rotation of the motor arranged in the body of themachine is transferred to a pipe spindle, and then to a shaft arrangedwithin the pipe spindle. With the cutting edge secured to the shaftbeing moved toward a workpiece (main line pipe), the boring machinedrills a hole. The cutting edge feeding mechanism including a chain isarranged side by side with the pipe spindle. The cutting edge feedingmechanism moves the shaft arranged in the pipe spindle toward theworkpiece while the cutting edge drills a hole in the workpiece. Aholder of the chain is slidably but non-rotatably supported on the outercircumference of the pipe spindle. The chain is secured to the holderwith both ends. Sprockets wrapped around by the chain are rotated by ahandle. The shaft is thus moved by the holder.

However, the above-described boring machine is subject to biting orbreaking of the cutting edge during drilling operation. Such troublesare likely to occur as below. When the handle is operated to lower theshaft having the cutting edge attached thereto, the handle and the shaftare directly linked to each other by the chain. In response to theoperation, the shaft is suddenly lowered, thereby being put into contactwith the workpiece (main pipe) with strong force. This causes the lackof the cutting force and thus results in the cutting edge to bite intothe workpiece and to be lodged there, or the cutting edge may be evenbroken.

Even if the handle operation is performed carefully, the cutting edgecan be locked or broken down when the torque of the cutting edge becomestoo high due to high torque of the motor.

The cutting edge of the known boring machine is secured to the end ofthe shaft using a mounting shaft, and the number of cutting edges istypically four with this type of machine. Load acting on each cuttingedge becomes large enough to break the mounting shaft.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aboring machine free from troubles caused by operations of a handle and amotor.

In accordance with a boring machine of the present invention, rotationof a motor arranged in a body of the machine is transferred to a pipespindle, and then to a shaft arranged within the pipe spindle. A cuttingedge feeding mechanism is arranged side by side with the pipe spindle.The shaft in the pipe spindle is moved toward a workpiece by the cuttingedge feeding mechanism. A cutting edge is mounted on a tip of an end ofthe shaft. A chain holder is supported slidably but non-rotatably on theouter circumference of the pipe spindle. A chain is fixed to the chainholder with both ends thereof anchored to the chain holder. A sprocketwrapped around by the chain is rotated by a handle. The shaft is thusmoved by the chain holder. The radius of rotation of the handle of thecutting edge feeding mechanism is set to be reduced so that the shaft isslowly moved.

The maximum torque of the motor rotating the shaft is reduced.

The number of cutting edges falls within a range of six to eight.

The shaft moves slowly because the radius of rotation of the handle isreduced for moving the shaft in the cutting edge feeding mechanism. Asdescribed above, the shaft moves slowly because the radius of rotationof the handle is reduced for moving the shaft in the cutting edgefeeding mechanism, thus a large torque is not applied to the cuttingedge, and the cutting edge is free from biting or breaking.

Since a drilling operation is performed with lower torque by controllingthe maximum torque biting or breaking of the cutting edge is prevented.

By increasing the number of cutting edges, cutting load per cutting edgeis reduced. The breaking of the mounting shaft is thus prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a boring machine of one embodiment of thepresent invention with a portion thereof of broken away;

FIG. 2 is a front view of the boring machine with a portion thereof ofbroken away; and

FIG. 3 is a partial side view of the boring machine attached onto asaddle corporation stop.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Boring machines of the preferred embodiments of the present inventionare described below with reference to the drawings. FIG. 1 is a sideview of the boring machine of one embodiment of the present inventionwith a portion thereof of broken away, FIG. 2 is a front view of theboring machine with a portion thereof of broken away, and FIG. 3 is apartial side view of the boring machine attached onto a saddlecorporation stop.

Referring to FIGS. 1 through 3, there are shown a boring machine 1, apipe spindle 2 rotatably supported within the boring machine 1, and ashaft 3 vertically slidably supported within the pipe spindle 2. Acutting edge 4 for cutting a water pipe is mounted to an end of theshaft 3 with a mounting shaft. A cutting edge feeding mechanism 5,employing a chain, vertically moves the shaft 3 through the pipe spindle2. A motor 6 rotates the pipe spindle 2 and the shaft 3 via a reductiongear train 8 in a gear box 7. A saddle bracket 9 is fixed on the lowerend of the body of the boring machine 1. The lower end of the shaft 3 isrotatably supported at the lower end thereof on a needle bearing 10 inthe saddle bracket 9. A saddle fixing nut 11, loosely fitted over thesaddle bracket 9, is used to fix the boring machine onto a saddlecorporation stop (S) secured to a water main pipe (H).

A shaft guide 12 is fixed to the shaft 3 by a C-clip 13. Two ends of theshaft guide 12 are received in longitudinal grooves 2 a verticallyformed in the pipe spindle 2. Pin guides 14 are attached to the ends ofthe shaft guide 12 and are slidably supported on the outer circumferenceof the pipe spindle 2. The pin guides 14 are also connected torespective ends of a pin 15 that penetrates through the top portion ofthe pipe spindle 2. Pin covers 16 are arranged on the outercircumference of the pin guides 14, and ball bearings 17 are pressfitted to the upper and lower portion of the pin guides 14. A chainholder 18 is slidably supported on the outer circumference of the pipespindle 2, and covers the pin guides 14, the pin covers 16, and the ballbearings 17. The chain holder 18 is fixed by a C-clip 19.

The shaft 3 is housed in the pipe spindle 2, and the longitudinalgrooves 2 a are symmetrically arranged in the pipe spindle 2 withrespect to the center axis of the pipe spindle 2. The shaft guide 12 andthe pin 15 are received in the longitudinal grooves 2 a in a manner suchthat the shaft guide 12 and the pin 15 are vertically slidable but notrotatable around. The lower end of the shaft 3 is slidably supported ona bushing 20 within the pipe spindle 2. The pipe spindle 2 is rotatablysupported on the upper end portion thereof on a needle bearing 21 and athrust bearing 22 on a main body cover 1 a. The pipe spindle 2 isrotatably supported at the lower end portion thereof on a ball bearing23 to the gear box 7 mounted on the lower portion of the boring machine1.

The cutting edge feeding mechanism 5 as a chain driving mechanism isarranged side by side in a standing condition. A chain 5 a has both endsthereof anchored to the chain holder 18 to be endless, and is wrappedaround a pair of sprockets 24 and 25 respectively arranged on the upperand lower portions of the boring machine 1. As shown in FIG. 2, theupper sprocket 24 is secured to a sprocket shaft 26. A gear 27 is alsosecured to the sprocket shaft 26 with a predetermined space allowed tothe upper sprocket 25. A handle shaft 28 is rotatably supported on theboring machine 1. A gear 29 formed on the handle shaft 28 is in meshingarrangement with the gear 27 of the sprocket shaft 26. A handle 30 ismounted onto the handle shaft 28. In the known art, the handle 30 has alength of about 130 mm, but in this embodiment of the present invention,the handle 30 has a length of about 100 mm to reduce the radius ofrotation of the handle. A brake mechanism 34 including a spring 31, abrake 32, a brake disk 33, etc. is built into the handle shaft 28. Thelower sprocket 25 is rotatably supported on a bushing 36 in a sprocketshaft 35 secured to the boring machine 1.

As shown in FIG. 1, a first gear 37 is attached to the lower portion ofthe pipe spindle 2. The first gear 37 is in meshing arrangement with anoutput shaft 38 of the motor 6 via the reduction gear train 8 in thegear box 7. With the rotary drive of the motor 6 rotating, the pipespindle 2 rotates at a reduced speed. The motor 6 is a compact type andoutputs a low torque in comparison with the known art with the maximumtorque thereof limited.

A reverse rotation prevention belt 39 functions as reverse rotationprevention means of the boring machine. A hook 40 of the reverserotation prevention belt 39 is anchored at an eye nut 41 connected tothe end of a bolt of the saddle corporation stop. The reverse rotationprevention belt 39 thus allows tension to work in a direction oppositeto the direction of slackness of the boring machine 1.

A drilling operation of the boring machine 1 thus constructed isdescribed below. The saddle corporation stop (S) is fastened to the mainline water pipe (H). The boring machine 1 is then mounted on the saddlecorporation stop (S) using the saddle fixing nut 11. The reverserotation prevention belt 39 is anchored at the eye nut 41. When themotor 6 is switched on, the first gear 37 is driven by the motor 6 viathe reduction gear train 8, and furthermore the pipe spindle 2 isrotated. With this rotation of the pipe spindle 2 causes the shaft 3 tobe also rotated, and the cutting edge 4 attached to the shaft 3 is alsorotated.

When the handle 30 is turned in this state, the gear 29 formed on thehandle shaft 28 is also rotated as well as the gear 27 in meshingengagement with the gear 29. The rotation of the sprocket shaft 26thereby causes the sprocket 24 to rotate. And thus, this rotation causesthe chain 5 a wrapped around the sprockets 24 and 25 to turn. When thechain 5 a turns, the chain holder 18 attached to the chain 5 a slidesdownward along the rotating pipe spindle 2. The pin guides 14 and theshaft guide 12 housed in the chain holder 18 also slide downward alongthe longitudinal grooves 2 a of the pipe spindle 2. The shaft 3 havingthe shaft guide 12 thereon moves downward while rotating at the sametime. The cutting edge 4 attached to the bottom end of the shaft 3 thendrills a hole in the main line water pipe (H). When the hole iscompletely drilled, pressure of running water in the water pipe acts onthe end surface of the shaft 3, thereby pushing the shaft 3 upward.Since the handle shaft 28 includes the brake mechanism 34, the cuttingedge 4 is free from being pushed upward. The handle 30 is not reverserotated.

During the hole drilling, the shaft 3 having the cutting edge 4 attachedthereto is lowered by operating the handle 30. The radius of rotation ofthe handle in the known boring machine is large. Depending on the mannerof operation, a high torque occurs, causing the shaft to suddenly belowered. The cutting edge is put into contact with the main line waterpipe with strong force. The cutting edge may bite into the workpiece ormay be broken. In accordance with the present embodiment, the radius ofrotation of the handle is reduced by shorten the length of the handle,and the shaft 3 is slowly lowered with low torque. The possibility ofedge biting and edge breaking is thus reduced.

With the compact motor used, the maximum torque is set to be modest.With low torque, hole drilling is performed. The biting of the cuttingedge into the workpiece with high torque is thus prevented. The entireboring machine is thus reduced in scale.

In contrast to the known boring machine employing four cutting edges,the boring machine of the embodiment of the present embodiment employssix to eight cutting edges. Cutting load per cutting edge is thusreduced. The possibility of breaking of the cutting edge mounting shaftis also reduced.

1. A boring machine comprising: a machine body; a pipe spindle freelyrotatably supported within the machine body; a shaft vertically slidablysupported through the pipe spindle; a cutting edge supported at one tipof the shaft with a cutting edge mounting shaft; a cutting edge feedingmechanism for vertically moving the shaft through the pipe spindle, thecutting edge feeding mechanism including a chain; a motor for rotatingthe pipe spindle and the shaft; and a saddle bracket arranged on a lowerend of the machine body.
 2. The boring machine according to claim 1,wherein the pipe spindle is rotatably supported at a top end thereof ona needle bearing and a thrust bearing at a machine body cover of anupper portion of the machine body, and rotatably supported at a bottomend thereof on a ball bearing in a gear box secured to a lower portionof the machine body, wherein the pipe spindle comprises a pair ofgrooves vertically extending in symmetry with respect to the center axisof the pipe spindle and houses the shaft therewithin.
 3. The boringmachine according to claim 1, wherein the shaft comprises: a shaft guidereceived in the grooves of the pipe spindle, the shaft guide includingpin guides respectively on two ends thereof, the pin guides slidablyengaged with an outer circumference of the pipe spindle, and fixing theends of a pin penetrating through a top portion of the shaft; a pincover arranged on an outer circumference of each of the pin guides; anda chain holder housing the pin guides and the pin covers and beingslidably supported on the outer circumference of the pipe spindle,wherein the shaft is slidably supported at a lower end thereof withinthe pipe spindle.
 4. The boring machine according to claim 1, whereinthe cutting edge feeding mechanism comprises: a chain holder arrangedside by side in a standing condition with the pipe spindle and slidablybut non-rotatably supported on an outer circumference of the pipespindle; a chain having two ends thereof anchored to the chain holder; asprocket wrapped around by the chain; and a handle for rotating thesprocket, wherein rotation of the handle causes the sprocket to rotate,thereby moving the chain holder and the shaft.
 5. The boring machineaccording to claim 4, wherein the cutting edge feeding mechanismcomprises: the chain holder; the chain having two ends thereof anchoredto the chain holder; a pair of upper and lower sprockets arranged to bewrapped around by the chain; a sprocket shaft supporting the uppersprocket; a handle shaft linked with the sprocket shaft via a gear; ahandle secured to the handle shaft; a brake assembly housed in thehandle shaft; and a sprocket shaft supporting the lower sprocket.
 6. Theboring machine according to claim 5, wherein a radius of rotation of thehandle is reduced so that the shaft slowly moves.
 7. The boring machineaccording to claim 1, wherein the motor comprises a supporting shaftwhich is engaged, via a gear train in a gear box, with a first gearfixed to the pipe spindle, wherein the pipe spindle and the shaft arerotated at a reduced speed by the motor.
 8. The boring machine accordingto claim 7, wherein the shaft is rotated at a lower torque with themaximum torque of the motor controlled.
 9. (canceled)
 10. The boringmachine according to claim 1, wherein the number of cutting edges to bemounted on the shaft falls within a range from six to eight.
 11. Aboring machine comprising: a machine body; a pipe spindle freelyrotatably supported within the machine body, wherein the pipe spindle isrotatably supported at a top end thereof on a needle bearing and athrust bearing at a machine body cover of an upper portion of themachine body, and rotatably supported at a bottom end thereof on a ballbearing in a gear box secured to a lower portion of the machine body,wherein the pipe spindle includes a pair of grooves vertically extendingin symmetry with respect to a center axis of the pipe spindle; a shaftvertically slidably supported through the pipe spindle, the shaftincluding a shaft guide received in the grooves of the pipe spindle, theshaft guide including pin guides respectively on two ends thereof, thepin guides slidably engaged with an outer circumference of the pipespindle, and fixing the ends of a pin penetrating through a top portionof the shaft, a pin cover arranged on an outer circumference of each ofthe pin guides, and a chain holder housing the pin guides and the pincovers and being slidably supported on the outer circumference of thepipe spindle, wherein the shaft is slidably supported at a lower endthereof within the pipe spindle; a cutting edge supported at one tip ofthe shaft with a cutting edge mounting shaft; a cutting edge feedingmechanism for vertically moving the shaft through the pipe spindle, thecutting edge feeding mechanism including a chain holder arranged side byside in a standing condition with the pipe spindle and slidably butnon-rotatably supported on an outer circumference of the pipe spindle, achain having two ends thereof anchored to the chain holder, a sprocketwrapped around by the chain, and a handle for rotating the sprocket,wherein rotation of the handle causes the sprocket to rotate, therebymoving the chain holder and the shaft; a motor for rotating the pipespindle and the shaft, wherein the motor includes a supporting shaftwhich is engaged, via a gear train in a gear box, with a first gearfixed to the pipe spindle, wherein the pipe spindle and the shaft arerotated at a reduced speed by the motor; and a saddle bracket arrangedon a lower end of the machine body.